Leak testing apparatus



p 1969 R. r. FITZPATRICK ETAL Re. 26,661

LEAK TESTING APPARATUS Original Filed April 23, 1965 7 Sheets-Sheet 1znr nous, Jr.

ATTORNEYS Sept. 9, 1969 R. T. FITZPATRICK ET 26,661

LEAK TESTING APPARATUS 7 Sheets-Sheet 2 Original Filed April 23. 1965TORS .VZPAR/CX E J "M4 ATTORNEYS ear 440a r P 9, 1969 R. T. FITZPATRICKET LEAK TESTING APPARATUS Original Filed April 25, 1965 7 Sheets-Sheet 34 5! i Ikk k.

m mm 5 Y m; m Nnm R E 0 VI m 4 A #0 m Y Sept. 9, 1969 nzp mc ET AL Re.26,661

LEAK TESTING APPARATUS Original Filed April 23, 1965 7 Sheets-Sheet 5 ag N\ Q? n 24 n U 0: we mm mm m Nw um. m m m ing A A u m R p 1969 R. T.FITZPATRICK LEAK TESTING APPARATUS 7 Sheets-Sheet 6 Original Filed April23, 1965 hm mw QAT QQ NQ INVENTORS RICHARD tF/rz/unv/c/r mar 4100a, Jr.

ATTORNEYS 5 Q m wk 80% Z b m q Q lfi- 1969 R. T. FITZPATRICK ET 26,661

LEAK TESTING APPARATUS Original Filed April 235. 1965 7 Sheets-Sheet 7 HH TAJ QR p 5 WI L W :3 my

v w w mvw w M 2. v l EECE \nN m wN Qmw "m": b mww III Qww Z! i T l I i lI i United States Patent Int. Cl. G01m 3/04 US. Cl. 73-40 27 ClaimsMatter enclosed in heavy brackets I appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

The present invention relates to an apparatus for testing parts forleaks and more particularly to improvements in apparatus of the typedescribed and claimed in our prior application Ser. No. 375,515, filedJune 16, 1964, and entitled, Leak Testing Method and Apparatus. Thepresent application is a continuation-in-part of our prior applicationSer. No. 424,741, filed Jan. 11, 1965, and entitled, Leak TestingApparatus.

The testing apparatus illustrated and described in our priorapplication, referred to above, has a station where parts to be tested,such as engine castings, are stopped as they are moved along a conveyor.The apparatus operates to close and seal openings in the castings toform a closed chamber therein. Valves in a fluid system operate tosupply a testing fluid under pressure to the closed chamber in the partbeing tested and to separate chambers in a measuring instrument having amovable diaphragm therebetween. After the fluid attains a predeterminedpressure in the system, the valves shut off the supply of fluid andsegregate one chamber of the measuring instrument from the other chamberconnected to the part being tested. Movement of the diaphragm, due to adifference in pressure resulting from a leak from the part being tested,operates through a transducer to produce a voltage directly proportionalto the difference in pressure. The voltage, in turn, is then utilized tocontrol an electric circuit for indicating whether there is a largeleak, at small leak or no measurable leak in the part.

The electric control circuit automatically controls the initiation ofthe testing steps and has branches with RC networks and semi-conductorcurrent control elements for timing the various testing steps. Thetiming branches When energized successively operate an indexingmechanism for actuating stepping switches to connect the variousbranches which control the valves to initiate the various testing steps,time the duration of the steps and indicate the results of the test.This prior leak testing apparatus operates in a very satisfactory mannerto test parts for leaks and has had commercial acceptance.

One of the objects of the present invention is to provide an improvedelectric testing apparatus of the type indicated which automaticallytests a part in a shorter period of time with accurate reproducibilitythan has been possible with prior leak testing apparatus.

Another object is to provide an improved electric testing apparatuswhich is more sensitive in detecting leaks and responds more quickly toindicate a leak than prior leak testing devices.

Another object is to provide an improved electric testing apparatuswhich reduces errors due to ambient conditions such as temperaturevariations and more quickly produces a stabilized condition for accuratemeasurement of a leak in the part being tested.

Another object is to provide an electric testing apparatus of the typeindicated which may be easily and quickly adjusted through a wide rangeto vary the magnitude of a leak that will be indicated.

Re. 26,661 Reissued Sept. 9, 1969 "ice Another object of the presentinvention is to provide an improved electronically controlled leaktesting apparatus with a minimum number of moving parts to reducehysteresis and chance of error due to mechanical failure.

Still another object of the present invention is to provide an improvedelectronically controlled leak testing apparatus for automaticallyperforming a leak testing operation which is of extremely simple andcompact construction, economical to manufacture and one which isextremely rapid and reliable in indicating a leak in a part beingtested.

These and other objects will become more apparent from the followingdescription and drawings in which like reference characters denote likeparts throughout the several views. It is to be expressly understood,however, that the drawings are for the purpose of illustration only andare not a definition of the limits of the invention, reference being hadfor this purpose to the appended claims.

In the drawings:

FIGURE 1 is a diagrammatic view of a production line conveyor at atesting station and showing the manner of clamping the part to be testedand sealing the cavities therein for a testing operation and the controlswitch for initiating a testing operation; and

FIGURE 2 is a diagrammatic view of a pneumatic testing system showingthe manner of connecting the cavity in a part to be tested forcomparison with a trapped sampie to indicate a difference in pressurewhen a leak occurs; and

FIGURE 3 is a perspective view of a cabinet in which the entire testingapparatus is incorporated; and

FIGURE 4 is a side elevational view of the cabinet illustrated in FIGURE3 with a side of the cabinet removed to show the arrangement of partsincluding a manifold block and measuring instrument; and

FIGURE 5 is a front view of the manifold block showing the location ofthe passageways forming conduits therein and the control valvestherefor; and

FIGURE 6 is a longitudinal sectional view taken on line 66 of FIGURE 5and showing the valves extending through the manifold block and inalignment with the passageways therein; and

FIGURE 7 is a sectional plan view taken on line 7--7 of FIGURE 5 to showthe divide valve in the passageways in the manifold block between theseparate chambers of the measuring instrument, the spherical form of thevalve and its actuator; and

FIGURE 8 is a transverse sectional view taken on line 88 of FIGURE 7 andshowing a type of fluid motor that may be used for actuating the valvesand a piston type control valve in section; and

FIGURE 9 is an enlarged sectional view taken on line 9-9 of FIGURE 7 toshow how the spherical valve element is mounted for rotary movement inits housing; and

FIGURE 10 is an exploded view of the parts of the valve to show theconstruction in detail; and

FIGURE 11 is a diagrammatic view of the measuring instrument forproducing voltage variations directly proportional to a difference inpressure; and

FIGURE 12 is a diagrammatic view of the electric circuit forautomatically initiating the successive steps of a testing operation andindicating the results of the test; and

FIGURE 13 illustrates a modified arrangement of the electric circuit inFIGURE 12 to show an additional circuit branch for indicating a largeleak; and

FIGURES 14 to 16 inclusive illustrates a manifold block of modifiedconstruction.

The present invention resides in a plurality of separate improvements inthe testing apparatus of our prior application Ser. No. 375,515 whichcooperate with each other to produce a substantial improvement in the apparatus as a whole. One of these features of improvement resides in theselection, construction and arrangement of elements to reduce the sizeand cost of the testing apparatus. Another feature of improvementresides in a pneumatic system which requires only three control valves,and simplifies the coring in the manifold block. Another feature is thekind of valves used and their arrangement in the manifold block whichavoid any displacement of the testing medium when operated. Anotherfeature is the close arrangement of the manifold block and measuringinstrument together with the mechanical valve actuators to reduce thepossibility of errors resulting from temperature differences atdifferent locations of the pneumatic system and heat conduction fromelectromagnetic windings of solenoid valve actuators. Another feature ofimprovement is the elimination of all mechanically operated switchesexcept the pressure operated switches. Another feature is the provisionof an improved electronic sensing circuit which is more sensitive to theoccurrence of small leaks. Still another major feature of improvementresides in the electronic control circuit in which the semiconductorcurrent control devices are used to time and control the steps of atesting operation without any delay. These and other features willbecome more apparent from the following description which result in anautomatically operable testing apparatus which is more sensitive indetecting a leak, more quickly responsive in indicating a leak, moreaccurate in indicating a leak and more reliable in operation thanpreviously known leak testers.

Referring now to the drawings, FIGURE 1 illustrates a conveyor 1 forintermittently advancing parts 2 to a station 3 where the parts are tobe tested for leaks. In the illustrated embodiment the parts 2 are shownin the form of automobile engine blocks having internal cavities in theform of cylinders and valve ports. At station 3 the engine block 2 isstopped by a ram 4 which engages its front end and clamps the blockagainst dogs 5 and 6 at its rearward end. Closures 7 and 8 are thenoperated to cover and seal openings, such as the valve ports and crankcase opening in the block, and the ram 4 has a seal 9 which also closesthe opening in the front end of the block for connection to a water pump(not shown). Closure 8 is shown diagrammatically as operated by anelectro-magnetic actuator 10 having an extension 11 which operates aswitch 12 to initiate a testing operation. While not shown, it will beunderstood that ram 4 and closures 7 and 8 are operated automatically insequential order and that the closure 8 will be the last to be actuatedso that all of the openings will be closed and sealed before switch 12is closed to initiate a test.

The testing apparatus is illustrated diagrammatically in FIGURE 2 ascomprising a fluid pressure system having a source of fluid 15 at highpressure, for example, air at 120 pounds per square inch. A conduit 16from the fluid source 15 has a filter 17 and pressure regulator 18therein for reducing the pressure from 120 pounds per square inch to 45pounds per square inch. Beyond the pressure regulator 18 is anormally-closed rapid-fill valve 19 and pressure operated switches 20and 21. The switches 20 and 21 are shown separately in FIGURES 2 and 12for purposes of description, but it will be understood that they may becombined in a single unit. Switch 20, referred to herein as the highpressure switch, is a double pole type having one normally-closedcontact 20a which opens at 35 pounds per square inch and onenormally-open contact 20b which closes when a pressure of, for example,45 pounds per square inch occurs in the conduit 16. Low pressure switch21 is normally-open above 35 pounds per square inch and closed at 35pounds per square inch and below. As thus far described, the apparatusis similar to that described and claimed in a prior pending applicationof Dewey M. Evans et al. Ser. No. 779,349 now Patent No. 3,221,539 andin our prior application Ser. No. 375,515, referred to above.

In accordance with the present invention a measuring instrument 24 isconnected to the conduit 16 beyond the low pressure switch 21 and theend of the conduit terminates in a ballast tank 25. The measuringinstrument 24 has separate cells or chambers 26 and 27 with a diaphragm28 therebetween and the chambers are connected to the line 16. A branch16a from the conduit 16 is connected to one of the closures 7 to supplyair under pres sure to the cavity in the engine block 2 and the oppositeside of the engine block is sealed by a closure 7a. Conduit 16 andbranch 16a are vented to the atmosphere through a branch 16b. Anormally-open divide valve 29 is provided in the conduit 16 between thebranches 16c and 16d connecting the conduit 16 to the separate chambers26 and 27 of the measuring instrument 24. Divide valve 29 when closedisolates the ballast chamber 25 and chamber 27 of the measuringinstrument from the remainder of the testing circuit including the otherchamber 26 of the measuring instrument and part to be tested. Anormally-open dump valve 30 is provided in the branch line 16b forventing the conduit 16 to the atmosphere. Thus, only the valves 19, 29and 30 are required to perform a testing operation.

To perform a leak test, the dump valve 30 is closed and the fill valve19 is opened to supply air at 45 pounds per square inch through theconduit 16 and branch 16a to the cavity in the engine block 2. The airsimultaneously flows into the ballast chamber 25 and chambers 26 and 27of the measuring instrument 24. If a pressure of 35 pounds per squareinch does not occur within a predetermined period of time due to a largeleak in the part, the contact 20a of the high pressure switch 20 doesnot open which immediately terminates the test. When a pressure of 45pounds per square inch does occur in conduit 16, the contact 20a doesopen and contact 20b of the high pressure switch 20 closes and operatingthrough a control circuit, later to be described, initiates the nextstep in the testing operation by closing the rapid-fill valve 19 andopening the dump valve 30. Dump valve 30 then bleeds testing fluid fromthe chambers 26 and 27 of the measuring instrument 24 and part 2 to betested until a low pressure of 35 pounds per square inch occurs in theconduit 16 and closes the low pressure switch 21. Switch 21 operatesthrough the control circuit to again close dump valve 30 and to trap theair at that pressure in the interior of the part to be tested for aperiod of time, as measured electronically, to permit the pressure tostabilize. The divide valve 29 is then closed to isolate the ballasttank 25 and chamber 27 of the differential pressure measuring instrument24 from the chamber 26 and cavity in the part 2 being tested. The dividevalve 29 is maintained closed for a predetermined period of time asmeasured electronically, for example, five seconds, during which timeany leak in the engine block 2 will produce a difference in pressure inthe chambers 26 and 27 of the measuring instrument 24 and a movement ofthe diaphragm 28 to the left as viewed in FIGURE 2.

The testing apparatus of the present invention provides an extremelycompact arrangement having a minimum number of elements which are allmounted in a cabinet 34, as shown in FIGURE 3. This cabinet 34 isportable and placed closely adjacent the station 3 of the conveyor, seeFIGURE 1, where the parts are to be tested. A fluid supply line 15, seeFIGURE 2, leads into the cabinet 34 to supply fluid thereto at poundsper square inch and the branch 16a leads from the cabinet to the closure7 for closing the parts to be tested. All of the other parts of thetesting apparatus are located in the cabinet 34 to reduce the length ofthe connecting lines therebetween to a minimum, and especially the lines16c and 16d between the measuring instrument 24 and the ballast tank 25.Due to the short lengths of the connecting lines between the elements,less time is required to stabilize the pressure throughout the testingsystem and a more accurate measurement may be made by any differencesresulting from a leak in the part being tested.

As shown in FIGURE 3, the front of the cabinet has three window openings35, 36 and 37 at the left hand side for indicating the particular stepsas the testing operation proceeds, such as fill" and stabilize and testand one of the three signs is illuminated during the test to indicatethe progress of a test. At the right hand side of the cabinet 34 thereare three other window openings 38, 39 and 40 with signs thereinindicating a large leak or a small leak" or accept and one of the threesigns will be illuminated after a test to indicate one of the threeconditions. Between the window openings in the center of the cabinet 34is a meter 41 for indicating a difference in pressure and the amount ofpressure difference resulting from a leak. A knob 42 of a controller 43,later to be explained in more detail, is provided for adjusting thepressure difference which the measuring instrument senses to indicate aleak. Another knob 44, which actually represents a plurality of knobs isprovided for adjusting the resistance of the RC networks of timingbranch circuits and thereby adjusts the period of time for a particularstep of the method.

The arrangement of the principal elements of the testing apparatus inthe cabinet 34 is illustrated in FIGURE 4 as comprising the meter 41,the controller 43 having knob 42, a manifold block 45 in which theconduits 16, 16a and 16b are formed as passageways, and the measuringinstrument 24. The other elements of the testing apparatus such as theair filter, pressure regulator switches 20 and 21 are not shown toprovide a clear illustration of those parts that are shown. In addition,the cabinet includes separate compartments for each of the windowopenings 35 to 37 and 38 to 40 which contain electric lamps 35L to 40L.Cards having printed circuits with the electronic elements mountedthereon (not shown) are located in the cabinet 34 forwardly of themanifold block 45. The electronic elements and the circuitsautomatically control the steps of a testing operation, as laterexplained in more detail.

The manifold 45 is in the form of a block of metal, such as aluminum,and is shown in detail in FIGURES 4 to 7. The manifold block 45 is ofrectangular shape and may be made as small as 9.5 inches high, 5.5inches wide and 2 inches thick. The ballast tank 25 is formed as acylindrical cavity bored in the block and closed by a plug 48 insertedin the open end as shown in FIGURES 5 to 7. The main conduit 16 of thefluid system in the manifold block 45 is formed by a vertical passagewaydrilled from the bottom edge of the block as shown in FIGURE 5. Branchconduit 16a is formed as a passageway in the manifold block 45 by a holedrilled into the block from the right hand side as shown in FIGURE 5 andinto the top of the ballast chamber 25. The horizontal extension ofbranch conduit 16a beyond the vertical main conduit 16 and into theballast cavity 25 becomes part of the main conduit 16. The branch 16b ofthe fluid testing circuit is formed by a passageway drilled into themanifold block 45 from the right hand side as viewed in FIGURE 5 untilit intersects the vertical passageway 16. Each of the passages 16, 16aand 16b are located midway between the front and rear of the block asshown in FIGURES 6 and 7. The open end of the vertical passageway 16forms a port 49 at the bottom of the manifold block 45 for connectionthrough an external pipe to the pressure regulator 18, the passage 16aprovides a port 50 for connection to the closure 7 of the workpiece 2 tobe tested by a flexible conduit and the passage 16b forms a port 51through which air is exhausted to the atmosphere. In addition, themanifold block 45 has passages 52 and 53 drilled from the rearward sideof the block as viewed in FIGURE 5 and directly into the ballast chamber25 and passageways 16a, respectively. Passages 52 and 53 provide ports54 and 55 for connecting the short lead conduits 16c and 6 16d to thechambers 26 and 27 in the measuring instrument 24, see FIGURE 2.

Another feature of the present invention is the kind and location ofvalves 19, 29 and 30 which project through the manifold 45 forcontrolling the flow of fluids therein and which open and close withoutdisplacing fluid on either side thereof. To this end, the manifold block45 has three tapered holes 56, 57 and 58 extending from the rear of theblock toward the front as viewed in FIG- URE S with cylindricalcounterbores 56a, 57a and 58a at the forward ends. correspondinglyshaped tapered valves 19, 29 and 30 extend through the manifold blockand have movable valve elements there in alignment with the passageways16 and 16b to be controlled. As all three of the valves are of identicalconstruction, a description of one should sufiice for the others.

Each of the valves 19, 29 and 30, as shown in FIG- URE 10', comprises aconical housing 60 with screw threads cut in its smaller end 61. A nut59 screwed on the threaded end 61 of the valve housing 60 in thecounterbore clamps the valve housing in position in its hole 56, 57 or58 in the manifold block. The valve housing 60 has a cylindrical bore 62of a size to receive a movable valve element in the form of a ball valve63. The rotating ball valve 63 also has a cylindrical bore 64 to providea passage for the flow of fluid therethrough and a slot 65 in itsperiphery located in a plane normal to the cylindrical bore 64. Mountedon either side of the ball valve element 63 are valve seats in the formof detachable rings 66 and 67 of an anti-friction material such asTeflon and have a conical surface 69 at one side corresponding to thetaper of the valve housing 60 and a spherical face at its opposite sidefor engaging the surface of the ball. A valve stem 70 extends through anaxial bore 71 in the bottom of the valve housing 60 and has a projectingkey 72 at its inner end for engaging the slot 65 in the ball valveelement 63 and a key 73 at its outer end for engagement with anactuator. In addition, the valve body 60 has ring gaskets 74 and 75 inperipheral grooves therein above and below the cylindrical bore 62.

As shown in detail in FIGURE 6, the tapered valves 19, 29 and 30 extendthrough the manifold block 45 and form a tight fit with thecorrespondingly shaped tapered holes 56, 57 and 58 in the block 45 andare fastened therein by the nuts 59 screwed onto the threaded nut 61 ofthe valve housing. Each valve housing 60 is sealed on opposite sides ofthe conduit which it controls by the gasket rings 74 and 75. The movableball element 63 of the valve is located in the valve housing 60 as shownin FIGURES 7 and 9 in alignment with the passage 16 in the block whichit controls and with the valve seat rings 66 and 67 in the cylindricalbore 62 of the valve housing engaging its opposite sides. When the ballvalve element 63 is moved to a right angular position from the full lineto the dotted line positions shown in FIGURE 9 the solid peripheralportions 77 and 78 of the ball overlie and close the passage 16. Theball valve element 63 is turned by its valve stem projecting outwardlyfrom the side of the manifold block 45 through the axial bore 71 of theconical housing 60, see FIGURE 10, which has its key 72 engaging thekeyway slot 65 in the ball element.

The valve stems 70 of the valves 19, 29 and 30 are rotated by amechanical actuator 80 such as a fluid operated motor. Such mechanicalactuators 80 do not produce heat as do magnetic windings which are aptto transfer heat to the manifold block 45 by conduction and vary thetemperature of the fluid therein from that in the remainder of thesystem and thereby affect the accuracy of the measurement of pressuredifferences. As shown in FIGURES 4 and 7 the fluid motor actuators 80are mounted directly on one side of the manifold block 45 with thedriving shafts 81 interlocked with the key 73 on the valve stem 70. Thefluid motor actuators 80 may have any suitable construction and in theillustrated embodiment as shown in FIGURE 8 comprise a cylindricalcasing 82 and vane type piston 83 forming chambers 84 and 85 at oppositesides thereof. Fluid supply conduits 86 and 87 are connected to thechambers 84 and 85, respectively, and the fluid to the chambers may becontrolled by any suitable control mechanism such as the piston typevalve illustrated in FIGURE 8. This piston type valve mechanismcomprises a cylindrical housing 88 to which the conduits 86 and 87 areconnected. A supply pipe 89 is connected to the center of the housing 88through which fluid under pressure is supplied thereto and exhaust pipes90 and 91 are connected to its opposite ends. The movable valve elementhas spaced pistons 92 and 93 fixed on a rod 94 and so arranged that inone position the pipe 89 is connected to conduit 86 and to the chamber84 in the motor between the pistons while the other conduit 87 isconnected to the exhaust pipe 91 at the opposite side of piston 93. Inthe other position of the piston valve the pistons 92 and 93 connectpipes 89 and 87 to supply fluid under pressure to the chamber 85 andconnect the chamber 84 and conduit 86 to the exhaust pipe 90. A spring95 acts between the end of the housing 88 and piston 93 to move it inone direction, such as that in FIGURE 8, and a solenoid winding 96 actson a valve stem 97 projecting from the housing to move the pistons 92and 93 to the right against the action of the spring.

In addition, the high and low pressure switches 20 and 21 areincorporated in an element 98 mounted on the side of the manifold block45, see FIGURE 5, and connected to the passageway 16 in the blockthrough the hole 99.

The measuring instrument 24 is also mounted on the rear of the manifoldblock 45 and closely adjacent thereto by the connections 16c and 16d aspreviously explained. The short length of the connecting conduits 16cand 16d reduce the length of the columns of air between the parts andthe measuring instrument as shown most clearly in FIGURE 7. The dividevalve 29 is positioned in a right angular extension of the conduit 16between the branch conduits 16c and 16d leading to the separate chambers26 and 27 of measuring instrument to isolate ballast cavity 25 andchamber 27 from chamber 26 and the part 2 to be tested. FIGURE 7 alsoshows the valve actuator 80 for the divide valve 29 on one side of themanifold block 45 and the measuring instrument 24 located closelyadjacent the other side so that by turning the ball element 63 of thevalve, the conduit 16 between the conduit branches 16c and 16d isclosed.

FIGURE 11 diagrammatically illustrates the measuring instrument 24comprising the chambers 26 and 27 at opposite sides of the diaphragm 28.At opposite sides of the diaphragm 28 are electrode plates 102 and 103mounted on stems in the side walls of the chamber and connected byelectric lines 104 and 105 to electrodes 102a and 103a in an envelopecontaining a gas ionized by an oscillating generator 106 [in the form ofa vacuum tube] for producing a 50,000 cycle alternating current. Thegenerator 106 ionizes the gas between the electrodes 102a and 103a andthe space between the electrode plates 102 and 103 and diaphragmconstitute capacitor and when the diaphragm 28 is centrally positionedbetween the plates the electrode plates are equally charged. However, asthe diaphragm moves to the left in FIGURE 11, due to a leak in the part2 to be tested, the plate 102 becomes more highly charged than plate103. This difference in charge on the electrodes 102 and 103 produces atransient current voltage as described in United States Letters Patentto K. S. Lion et Nos. 2,696,556 and 2,696,584 issued Dec. 7, 1954, andentitled "Electric Transducer System and Electric Circuit respectively,which is directly proportional to the degree of displacement of thediaphragm 28 which, in turn, is directly proportional to the differencein pressure in the chambers 26 and 27. Thus, the measuring instrument 24constitutes a transducer which converts mechanical movement to anelectric potential. The change in potential, due to deflection of thediaphragm 28, is converted into a current flow by the cathode follower107 which, in turn, is connected to an electric bridge 108. The bridge108 has resistances 109 and 110 connected to opposite sides of outputlines 111 and 112 of the cathode follower 107 which are connected toeach other at the junction 113, and a variable resistance 114 across theline has a tap contact 115. Variable resistance 114 and its tap contact115 form, in effect, an adjustable potentiometer. Thus, any transientvoltage generated will be transmitted from the bridge through lines 116and 117 from the tap contact 115 and junction 113. This ditierence involtage is used to automatically indicate a leak in the part beingtested. The position of the tap contact 115 of the bridge 108 may beadjusted by the knob 42 as previously described, see FIGURE 3, and thefurther toward the line 111 that the tap is initially adjusted, asviewed in FIGURE 11, the larger will be the leak that can be detected.In addition, the meter 41 is connected across the lines 111 and 112 andWill indicate a leak visually.

FIGURE 12 diagrammatically illustrates the electric circuit of thepresent invention for automatically initiating and controlling theperformance of the steps of an entire testing operation. The steps ofthe testing operation are performed in a predetermined timed sequenceand all mechanical switches except the pressure operated switches 20 and21 are eliminated to increase the speed with which the testing steps areperformed and to increase the reliability of operation. The controlelements are all of the solid state type comprising semiconductors whichresist the flow of current until energized by an electric pulse and thenfire to permit current flow until the gate or emitter becomes negativeat which time they again resist and shut oif the flow of current. Thesemiconductor current control devices used in the control circuitinclude silicon control rectifiers which are fired at a predeterminedthreshold voltage and continue to conduct after once started, andunijunctional transistors which are much more critical to an impressedstarting and stopping voltage at which they conduct and shut off currentflow. The control elements also include silicon control diodes whichpermit flow of electric current in one direction only to protect therectifiers and transistors.

The circuit, in general, comprises a plurality of branches connected inparallel between lines L1 and L2 of a DC source as, for example, 24volt. Certain of the branch circuits comprise a plurality of timing RCnetworks 120, 121 and 122 corresponding to the filling, stabilizing andtesting steps, each of which require a predetermined period of time;current responsive branches of actuating instrumentalities, such asvalves 19, 29 and 30 required for performing the testing steps; currentresponsive branches for indicating the various steps of the testingoperation; current responsive branches for indicating the results of thetest; and the interconnections between the various branches to energizethe timing and current responsive branches in the proper timed sequenceand for indicating the various steps of the testing operation andresults of the leak test. In the following description the value of theresistors R and capacitors C used in a particular circuit will be given,but it will be understood that these values may be changed forparticular installations.

The timing branches 120, 121 and 122 for controlling the timed periodfor filling, stabilizing and testing, respectively, are identical sothat a description of the one for controlling the filling operation, andindicated by the subscript (1), will suffice for the others. The RCnetwork for the timing branch 1, for example, includes a variableresistor R-lb of 100,000 ohms and a capacitor C-1 of 50 microfarads. Thevariable resistor R-lb is adjustable by turning knob 44, see FIGURE 3,to vary the time period for filling between, for example, I and seconds.The resistor R-lb and capacitor Cl are connected in series across the 24volt line and the emitter E of a unijunctional transistor T1 isconnected between the resistor and capacitor. Balancing resistors R-lcand R-ld of 270 and 50 ohms, respectively, are connected between thebases B-1 and B-Ia of transistor T-1 and opposite sides of the line. Theelements of the timing branches 121 and 122 are indicated by the samereference characters as the timing branch 120 with subscript 2 and 3,respectively. Each of these timing branches takes a predetermined periodof time to charge the capacitor to the potential at which transistorconducts current.

A current responsive indicating device such as an electric lamp 35L,36L, 37L is connected in parallel with each timing branch 120, 121 and122, respectively, for illuminating the signs indicating the fill,stabilize and test steps.

All of the other current responsive devices are connected in parallelbranches, generally designated 4 to 13,

- between the lines L-l and L-2 and these branches include control aswell as current responsive devices. For example, the solenoid coils foroperating the fill valve 19, divide valve 29 and dump valve 30 areconnected in branch circuits Nos. 4, 7 and 6, respectively, and areindicated by reference characters S-19, S-29 and 8-30. Also currentlamps 38L, 39L and 40L for indicating the result of a test are shownconnected in branch circuits 11, 12 and 13. Thus, when any of the lamps38L, 39L or 40L is energized it will illuminate the sign incorresponding window 38, 39 or 40 in the cabinet 34, see FIGURE 3, toshow a large leak, a small leak or an accept signal.

A leak sensing circuit branch 123 responsive to variations in theelectrical output from the measuring instrument 24 and bridge circuit108, see FIGURE 11, is connected between the branch 122 for timing atest period and the current responsive branch 12 including the indicatorlamp 39-L for indicating a small leak. The sensing circuit comprises aunijunctional transistor T-14 having an emitter E-14 connected to thetap 115 from the bridge circuit 108 through a line including adirectional diode D-l4 and capacitor C14 of 0.2 microfarad connected inseries. One end of the line is connected to output line 117 fromgenerator 106 at the junction 113 of the bridge 108 and including aresistor 118 of 10,000 ohms and the op posite end of the line isconnected to line L-l. Output line 117 also is connected to a secondcapacitor C14a of 0.01 microfarad in parallel with capacitor C14 andbetween diode D-14 and capacitor C14a the line is connected to theemitter E-14 of the transistor T-14. Transistor T-14 has a circuitincluding balancing resistors R-14 and R-l4a of 5,000 ohms each and avariable resistor R-14b of 5,000 ohms therebetween and connected betweenbranch circuit 3 and line L-1. Resistors R-14c and R-14d of 270 and 100ohms, respectively, are connected between the bases of the transistorT14 and output from branch 3 and line L-l in parallel with resistorsR-14 and R-14a. Also in parallel with the resistors and across the lineincluding the transistor T-14 is a voltage regulator VR-14 to maintain aconstant voltage difference applied to the opposite bases of thetransistor. A resistor R-14f of 470 ohms is connected between transistor circuit and the branch circuit 3.

The circuit will now be described by the functions it performs so thatin addition to describing the circuit the mode of operation of thetesting apparatus also will be described. When a part 2, such as anengine block, engine head, manifold or any other part having a cavity,see FIGURE 1, is to he tested for leaks it is brought into place at thestation 3 and sealed and the movement of closure 3 actuates the startswitch 12 to initiate operation of the leak testing apparatus. As shownin FIGURE 12, the start switch 12 is normally connected to the oppositeside of the line through a resistor R15 to charge the capacitor ClS.When the switch 12 is actuated by closure operator 11, the charge in thecondenser ClS will be directed as an electric pulse through line 124 and124a to resistor R10 of 1,000 ohms and diode D-10 of branch circuit 10to the gate G of silicon control rectifier Q10 therein. Pulsing ofrectifier Ql0 causes it to fire and produce current flow from line L2 toL-1 through the branch 10 including resistor R-l0b of 1,000 ohms. Branch10 also includes a resistor R-10a of 1,000 ohms to protect the rectifierfrom reverse flow through the branch. Current flow through branch 10charges capacitors Cll, C-12 and C13 of 3.0 microfarads each which putsa negative bias on the silicon control rectifiers Q-ll, Q-12 and Q-13 inbranches 11, 12 and 13 to shut off current flow therein. Thus, all lamps38L, 39L and 40L in the branches I1, 12 and 13 will be extinguished.

Simultaneously, a pulse will be directed from line 124a to gate G ofsilicon control rectifier Q9. When rectifier Q9 fires current will flowthrough branch 9 including resistor R9 of 1,000 ohms to connect line L-2to its extension L-2a. Thus, one end of all of the branches 1 to 8 willbe connected to line L-2. Branch 9 also includes resistances R-9a andR-9b of 1,000 ohms each.

Also, the pulse from line 124a will be directed to the gates G ofsilicon control rectifiers Q4 and Q6 in branches 4 and 6 havingresistors and diodes the same as in branch 9. Firing of rectifiers Q4and Q-6 produces a current flow through the branches 4 and 6 includingthe solenoid windings S49 and 8-30 for operating the fill valve 19 toopen position and the dump valve 30 to closed position, see FIGURE 2.

Lastly, the actuation of switch 12 directs a pulse through line 124b tothe gate G of the silicon control rectifier Ql through resistor R-l of1,000 ohms and the isolating diode D-l. Firing of rectifier Ql producesa current fiow through the electric lamp 35-L to indicate that a fillingstep is being performed. Branch 1 has a resistor R-la of 1,000 ohms toprotect the rectifier Q-l, the same as branches 4, 6 and 11 to 13. Thefiring of the rectifier Q-1 also energizes the RC network of timingbranch 120.

With the fill valve 19 and divide valve 29 open and dump valve 30closed, air under pressure flows through the conduits 16 and 16a, seeFIGURE 2, to fill the chambers 26 and 27 of the measuring instrument 24,ballast tank 25 and cavity in the part 2 being tested. If the part 2being tested has a large leak which prevents an increase in pressure inthe conduit 16 Within, for example, 5 sec onds, transistor T-l of thefirst timing device fires and transmits a pulse through the lineconductor 127 and contact 20a of the pressure responsive switch 20 andthen through the resistor R1l and diode D-11 to the gate G of a siliconrectifier Q-ll in the branch circuit including the electric lamp 38-L.This branch circuit 11, like the others, has resistance R1la of 1,000ohms and a resistance R-llb of 47 ohms. Firing of rectifier Qll causescurrent flow through the electric lamp 38L to illuminate the signindicating a large leak in the part being tested. Current in branch 11also flows through the isolating diode D-lla and line conductor 128 togate G of a silicon control rectifier Q8 in branch 8. This branchincludes resistances R-Sa and R-8b of 1,000 ohms and is connectedthrough capacitor C9 to the branch 9 circuit including the rectifier Q9.Current flow through the branch 8 changes the potential in the branch 9and shuts off the flow of current through the latter. Such interruptionin the current flow from the line L-2 to its extension L-2a opens thebranches 1 to 7 including the solenoid windings 8-19 and 8-30.Deenergization of solenoids 5-19 and 5-30 closes the fill valve 19 andopens dump valve 30. In other words, all of the branch circuits arereturned to their initial positions except 11 which remains energizedand indicates a large leak.

If after initiation of a test the pressure of the testing fluidincreases sufficiently to open the contact 20a of the switch 20 beforethe transistor T-l of the timing circuit 120 times out and fires, thebranch circuit 11 will not become energized which indicates that nolarge leak exists in the part 2 being tested. Contact 20b of thepressure switch 20a is normally connected through the resistance R-16 of1,000 ohms to capacitor C-16 of 3.0 microfarads and when actuated by theincrease in pressure to engage its other contact it transmits anelectric pulse from capacitor C-16 through the line 129 to gate G of thesilicon control rectifier Q-2 in branch No. 2 to cause it to fire andlight the lamp 36-L indicating a stabilizing step. Current flow inbranch 2 acts through a line 130 between branches 1 and 2 having acapacitor C-1a of 3.0 microfarads which produces bias on branch 1 andshuts off current flow therein and extinguishes lamp 35-L. Firing of therectifier Q-2 also energized the RC network of timing circuit 121.

Simultaneously, contact 20b of the pressure switch 20 delivers anelectric pulse through the line 128a to gate G of the silicon controlrectifier Q to produce a flow of current to branch circuit 5. Branchcircuit 5 is connected to the branch circuits 4 and 6 through capacitorsC-4 and C-6 of 3 microfarads which produces a negative bias on therectifiers Q-4 and Q-6 to shut off current flow in these branches. Theinterruption of current flow in branches 4 and 6 deenergizes the solidwinding 8-19 to close the fill valve 19 and solenoid 8-30 to open thedump valve 30.

Pressure fluid then bleeds from the pressure testing system through theopen dump valve 30 until the pressure falls to some lower pressure of,for example, 35 pounds per square inch at which time the contact of theswitch 21 is actuated. Switch 21 in its high pressure position isconnected to the positive side of a powerline through a resistance R-17of 1,000 ohms to charge a capacitor C-17 of 3.0 microfarads. When theswitch 21 is actuated to the lower pressure position, capacitor C-17delivers a pulse through the line conductor 131 to gate G of the siliconcontrol rectifier Q-6 in branch 6 including the solenoid S30 for thedump valve 30. Firing of the rectifier Q-6 energizes the solenoid 8-30to again close the dump valve 30.

A predetermined time period after Q-5 fires to close the dump valve 30and the fluid pressure has become stabilized throughout the system, theRC network of the stabilizing branch 121 will produce a voltage on theemitter E of the transistor T-2 which will cause it to fire. Firing ofthe transistor T-2 produces a current flow through the line conductor132 to the gate G of the silicon control rectifier Q-3 in branch 3 tocause it to fire and conduct current through the lamp 37-L indicatingthat a testing step has been initiated. Firing of the rectifier Q-3first sends a pulse through the line 133 to the condenser C-2a to put abias on the rectifier Q-2 and stop current flow through the lamp 36-L.Firing of rectifier Q-3 also energizes the RC network of the timingcircuit 122. Firing of the rectifier Q3 also delivers a pulse throughline 134 to the gate G of rectifier Q-7 causing it to fire and conductcurrent through branch 7 including the solenoid 8-29 of normally-opendivide valve 29 (see FIGURE 2). Closing of divide valve 29 thensegregates the ballast tank 25 and chamber 27 of the testing element 24from the remainder of the pneumatic testing system so that the oppositechamber 26 of the testing element is connected to the cavity in the part2 being tested. Firing of the rectifier Q-3 also directs current throughthe branch line 134a and resistanoe R-l4f to energize the sensingcircuit including the transistor T-14.

Any deflection of the diaphragm 28 of the measuring device 24 resultingfrom a small leak in the part being tested produces a transient voltagein the cathode follower 107, see FIGURE 11, and thereby produces adifference in potential between the lines 116 and 117 which is impressedon the emitter E of the transistor "IT-14. When this potential rises toa predetermined value for which it is set the transistor T-14 fires andproduces a current flow through the line 135 to the gate 6 of thesilicon control rectifier Q-12 to cause it to fire. Firing of therectifier Q-12 produces a current flow through the branch 12 includingthe lamp 39L to indicate that a small leak exists. Branch circuit 12 hasa resistance R12b of 47 ohms between the rectifier and side L2 of theline and a parallel line is connected through a diode D-12a to theconductor 128. A pulse is then transmitted through line 128 to gate G ofrectifier Q-S in branch 8 and acting through the capacitor C-9 shuts offthe current flow through branch 9 and thereby disconnects the extensionL-2a from line L2. Deenergization of line L2a returns all of thecircuits 1 to 8 and instrumentalities actuated thereby to their initialposition.

If no leak exists in the part being tested, no transient current isproduced in the sensing circuit, see FIGURES 11 and 12, so that no pulseis transmitted to the emitter of the transistor T14 in the testingcircuit sufiicient to cause it to fire. When the transistor T-3 in theRC timing circuit 122 fires, a pulse is transmitted through the lineconductor 136 to the gate G of the rectifier Q-13 in the branch circuit13. Rectifier Q-13 then fires conducting current through the lamp 40Lindicating no leak in the part 2 being tested. Branch circuit 13includes a resistance R-13b of 47 ohms between the rectifier Q-13 andopposite side of the line L-l and in parallel with the resistance R-31bis a line connected to the line 128 for firing the rectifier Q-8 inbranch 8 to interrupt current flow from the line L2 to extension L-2a,as previously described, to terminate the testing operation. All of thebranches Q-l to Q-9 are then deenergized and the elements controlledthereby are returned to their initial position. Upon deenergization ofthe branches 6 and 8 the dump valve 30 and divide valve 29 open toreduce the pressure in the fluid system to zero at which time thepressure switches 20 and 21 are returned to their initial position,illustrated in FIGURES 2 and 12. The only circuit which remainsenergized is the one indicating that the part has no leak. The testingapparatus will remain in this condition until the next part to be testedis moved into the testing zone 3 to again actuate the switch 12 toinitiate another test.

FIGURE 13 illustrates a modified circuit diagram which provides anadditional circuit branch for indicating a leak in a part being tested.On rare occasions a part may have a leak which is small enough to causethe high pressure switch contact 20a to open, but permit a suflicientamount of the fluid testing medium to escape during stabilization toapproach atmospheric pressure at the time the divide valve 29 closes.The pressure in the cells 26 and 27 of the measuring instrument 24 thenwill be equal and therefore, will not indicate a small leak.

The modified circuit arrangement illustrated in FIG- URE 13 willindicate such intermediate leaks as well as large and small leaks. Thecircuit arrangement illustrated in FIGURE 13 is identical with thatillustrated in FIG- URE 12 except that an additional branch line 200 isprovided between the rectifier Q-2 for energizing the stabilizingcircuit 2 and rectifier Q-11 in the responsive circuit 11 for indicatinga large leak. Included in the branch 200 is a resistance R-200 of 2200ohms and a low pressure switch 21a which closes at some pressure belowthe pressure at which switch 21 closes as, for example, 30 pounds persquare inch. For purposes of illustration the low pressure switch 21a isshown as one contact of the low pressure switch 21, but it will beunderstood that it could be a separate switch.

Thus, if the pressure of the testing fluid maintains switch contact 20aopen during a filling operation and operates switch contact 20b toenergize the stabilizing branch 2, but during the period ofstabilization the pressure in the system falls below 30 pounds persquare inch, the switch contact 21a will close. Closure of the switchcontact 21a completes a circuit through the branch 200 to pulse siliconcontrol rectifier Q-ll. Firing of rectifier Q11 energizes the responsivecircuit including lamp 38L to indicate a large leak. In other words, thebranch cir- 13 cuit 200 is connected in parallel with the line conductor127 to the rectifier Q-ll so that failure of the pressure testing mediumto open high pressure switch contact 20a or to maintain low pressureswitch contact open will indicate a leak.

FIGURES 14 to 16 illustrate a manifold block 245 of modifiedconstruction which further reduces the time required to stabilize at afixed pressure, reduces the number of turns in the tortuous paths offlow of the testing fluid as well as the length of paths, reduces thepossibility of surging, provides a more symmetrical arrangement andsimplifies the construction for manufacture. The block 245 has passages216, 216a and 216b the same as 16, 16a and 16b in FIGURE 5, openings249, 250 and 251 in the edges of the block the same as openings 49, 50and 51 in FIG- URE 5, valves 219, 229 and 230 the same as valves 19, 29and 30 in FIGURE 6 and a ballast cavity 225 the same as cavity 25 inFIGURE 5. However, the passages, openings, valves and ballast cavityhave a different arrangement and relationship in FIGURES 14 to 16 thanthey do in FIGURES 4 to 7.

In the modified arrangement illustrated in FIGURES 14 to 16 passageways216 and 216b are drilled as one hole lengthwise of the block 245throughout its length. The cavity 225 is drilled in the block inparallel relation to the passageway 21.6. With this modified arrangementthe end of the cavity 225 is closed by a cover plate 248 attached to theblock by screws 246 and having an O-ring seal 247 between the cover andblock. A third passageway 216a is drilled through the manifold block 245in a direction transversely of the passageways 216 and 225 andintercepts the latter passageway. Passageway 216a is connected to thepart to be tested and the passageway 216b is connected to the atmospherethe same as in FIGURES 2 and S; and the fill valve 219 extends throughthe block transversely of passageway 216, the divide valve 29 is locatedin passageway 216a between the part to be tested and the cavity 225 andthe dump valve 230 is located in passageway 21 6b. Passageways 216s and216d extend through the manifold block 245 into the passageway 216a atopposite sides of the divide valve 229.

With the modified manifold block 245 of FIGURES 13 to 15 testing mediumsupplied through the fill valve 219 is divided at the junction betweenpassages 216 and 216a and flows in two directions to the part beingtested and ballast chamber 225. The testing medium enters the ballastchamber 225 at the center and fiows toward opposite ends so that anysurging will occur only in the chamber. When the dump valve 230 isopened the testing medium flows from the ballast chamber 225 and partbeing tested toward each other and then out through passageway 216a tofurther reduce surging during stabilization period. The central locationof the divide valve 229 at the approximate center of th manifold block245 also reduces any variations in temperature at the place wherepressure variations are being measured. The arrangement of passages 216,216a and 216b in the manifold block 245 reduces the length of thepassages and number of turns in the paths of flow. Furthermore, thearrangement reduces the number of holes which must be drilled in theplane of the block to three to reduce the cost of manufacture.

It will now be observed that the present invention provides an improvedleak testing apparatus which is more sensitive in detecting leaks morequickly responsive to indicating a leak. It will also be observed thatthe apparatus of the present invention will automatically test a part ina shorter period of time with excellent reproducibility than has beenpossible with prior leak testing apparatus. It will further be observedthat the present invention provides an improved electric testingapparatus which reduces errors resulting from variations in the ambientand produces a stabilized condition more quickly for accuratemeasurement of any leaks in the part being tested. It will also beobserved that the present invention provides an electric testingapparatus which may be easily and quickly adjusted to vary the magnitudeof a leak to be indicated. It will further be observed that the presentinvention reduces the number of moving parts to a minimum and therebyreduces the hysteresis to thereby reduce the chance of error due tofailure of mechanically moving mechanisms. It will still further beobserved that the present invention provides a leak testing apparatusfor automatically performing a leak testing operation which is ofextremely simple and compact construction, economical to manufacture andone which is extremely rapid and reliable in indicating leaks in thepart being tested.

While several embodiments of the invention are herein illustrated anddescribed it will be understood that changes may be made in theconstruction and arrangement of elements without departing from thespirit and scope of th invention. For example, the electronic timing,sensing and responsive circuits for controlling a testing operation andindicating results can be used in other testing apparatus havingdifierent combinations and arrangements of ele ments as by providingseparate chambers for the valves and ballast tank instead of mountingthem all on the manifold block. Therefore, without limitation in thisrespect the invention is defined by the following claims.

We claim:

1. An apparatus for testing parts for leaks comprising a measuringinstrument having separate chambers with a diaphragm therebetween, asource of fluid under pressure, a manifold block having passages and aballast chamber therein, one of said passages connecting the source ofpressure fluid to the ballast chamber, a second passage connecting saidone passage to a closed chamber on the part to be tested, a thirdpassage connecting the first passage to the atmosphere, fourth and fifthpassages connecting the separate chambers of the measuring instrument tothe first passage adjacent to the ballast chamber, a normally closedfill valve in the first passage for filling all of the passages with atesting fluid from said pressure source when the valve is open, anormally open divide valve in said first passageway between the fourthand fifth passages to isolate one chamber of the measuring instrumentand ballast chamber from the remainder of the system, a normally opendump valve in the third passage for sealing the system when closed anddumping air from the system when open, said valves extending through themanifold block and having rotary valve elements in alignment with thepassages which they control, a mechanical valve actuator for each valve,pressure operated switches connected to the first passage in saidmanifold block, a sensing mechanism having a transducer for producing anelectric potential in a branch circuit proportional to any movement ofthe diaphragm in said measuring instrument, and an electric controlcircuit having timing branches for timing the steps of filling,stabilizing and testing, circuit branches including electric solenoidsfor controlling operation of the valves, circuit branches having currentresponsive indicating devices for indicating the results of the test,connections between the timing branches, current responsive branches andsensing branch, and each of branch circuits having solid statesemiconductors for controlling current flow therein.

2. An apparatus for testing parts for leaks comprising a measuringinstrument having separate chambers with a movable diaphragmtherebetween, a ballast chamber, a source of fluid under pressure,conduits connecting said chambers, a fill valve for controlling thesupply of fluid from said source to the separate chambers of themeasuring instrument, ballast chamber and part being tested, a dividevalve for isolating one of the chambers of the measuring instrument andballast chamber from the other chamber of the measuring instrument andpart being tested, a dump valve for exhausting fluid from all of thechambers to the atmosphere, a sensing mechanism having a transducer forproducing an electric potential in a branch circuit proportional to anymovement of the diaphragm resulting from a difference in pressure in thechambers of the measuring instrument, and an electric control circuitcomprising timing branches each having an RC network and solid statesemiconductor, means responsive to the firing of the solid statesemiconductor of each RC network at the end of its timing period topulse the semiconductor element in the RC network of the next branch fortiming the steps of filling, stabilizing and testing, current responsivebranches including elements for controlling operation of the valves andindicating the results of the test, each of said responsive branchcircuits having a solid state semiconductor for controlling the currentflow therein, and the semiconductors in at least some of the currentresponsive branches being electrically connected to be pulsed by thetiming branches to automatically fill, stabilize and leak test the partfor leaks.

3. Apparatus for testing parts for leaks in accordance with claim 2 inwhich the valves have rotary valve elements to open and close conduitswithout displacement of fluid therein, and a mechanical valve actuatorfor each of the valves.

4. In an apparatus for testing parts for leaks of the type including ameasuring instrument having separate chambers with a diaphragmtherebetween, a source of fluid under pressure, conduits connecting thesource of fluid to the chambers of the measuring instrument and a cavityin the part being tested, valves for filling the chambers, stabilizingthe fluid pressure therein and then isolating one of the chambers of themeasuring instrument from the other chamber and cavity in the part beingtested, that improvement comprising a sensing mechaniism having atransducer for producing an electric potential proportional to anymovement of the diaphragm in said measuring instrument, an electriccircuit having a sensing branch with a solid state semiconductorconnected to the transducer, said solid state semiconductor beingnonconductive until an electric potential is impressed thereon, aresponsive branch having a solid state semiconductor and an electricresponsive indicator therein, said semiconductor in the responsivebranch being nonconductive until an electric potential is impressedthereon, connecting means between the sensing branch and responsivebranch of the electric circuit whereby an electric potential from thesensing branch suflicient to fire the semiconductor therein impresses apotential on the semiconductor in the responsive branch to cause it tofire and produce a current flow in the electric responsive circuit, anda circuit branch having an RC network connected to the sensing branch tocontrol the time period during which its semiconductor can fire andproduce a current flow in the responsive branch.

5. An apparatus for testing parts for leaks of the type comprising amanifold block of a heat conductive material and having a ballastchamber formed therein, a measuring instrument having separate chamberswith a diaphragm therebetween and located adjacent said manifold block,a source of fluid under pressure, conduit means connecting said elementscomprising a first conduit in said block for connecting said source offluid to said chambers of the measuring instrument and part beingtested, a second conduit in said block for connecting said first conduitto the atmosphere, a fill valve in said first conduit in said block forcontrolling the supply of fluid from said source to all of the chambers,a divide valve for isolating one of said chambers of the measuringinstrument and ballast chamber in the manifold block from the otherchamber of the measuring instrument and part being tested, a dump valvein the second conduit for controlling the exhaust of testing fluid fromthe chambers, said manifold block having a front, back and sides, theconduits in said block being formed by holes drilled in said block fromthe sides, and the valves extending through the block from the front toback in alignment with the conduits therein. I

6. An apparatus in accordance with claim 5 in which the valves aretapered from one end to the other and seated in correspondingly shapedtapered holes through the manifold block, and sealing means including ascrew threaded fastener for clamping each valve in its seat in theblock.

7. An apparatus in accordance with claim 5 in which each valve comprisesa valve element mounted for rotation relative to the block and having anopening therein in alignment with the conduit in said block, and meansfor rotating the valve element to close the conduit without displacingany fluid in the conduit.

8. An apparatus in accordance with claim 7 in which each valve comprisesa tapered housing set in a correspondingly shaped tapered hole throughthe block, said housing having right angular holes therein, one of theholes in the housing being aligned with the conduit in the block and theother hole extending from the first hole outwardly from the block, saidvalve element comprising a sphere located in one of the holes in saidhousing and having a cylindrical hole therein in alignment with theconduit to be controlled and a slot in its periphery, sealing ringsbetween the spherical valve element and holes in the housing, and avalve stem in the other hole in the housing and engaging the slot in thespherical valve element for rotating the latter.

9. An apparatus in accordance with claim 7 in which a pneumatic actuatoris provided for each valve, and an electromagnetically operated controlvalve for each pneumatic actuator.

10. In an apparatus for testing parts for leaks of the type includinginstrumentalities to first fill the part to be tested with a fluid underpressure, stabilize the pressure in said part and then test the part forleaks in a predetermined timed sequence, that improvement whichcomprises an electronic circuit for timing and initiating operation ofthe instrumentalities comprising a plurality of RC timing networks, onefor each of the steps to be performed, a semiconductor control deviceconnected to each network which fires a predetermined period of timeafter energization of its network, each control device being connectedto energize a branch circuit having an instrumentality therein, andmeans for energizing the first network to cause the instrumentalities tobe operated in succession in a predetermined timed relation forautomatically testing the part for leaks.

11. In an apparatus for testing parts for leaks including a closure forforming a sealed chamber in the part to be tested, a measuringinstrument having separate chambers and a movable diaphragm forindicating a difference in pressure in said chambers, a source of fluidunder pressure, conduit means connecting said source of fluid pressureto the separate chambers of the measuring instrument and the sealedchamber in the part to be tested, a fill valve in said conduit means forcontrolling the flow of fluid from said source to the chambers of themeasuring instrument and chamber of the part being tested, a dividevalve in said conduit means for segregating one of the chambers of themeasuring instrument from the other chamber and chamber in the partbeing tested, means responsive to movement of the diaphragmcorresponding to a difference of pressure in the separate chambers ofthe measuring instrument, and an electric circuit for controllingoperation of the valves in succession, that improvement in said electriccircuit comprising a plurality of RC networks, one for each of thesuccessive steps of filling, stabilizing and testing, each networkincluding a semiconductor current control element which fires apredetermined period of time after energization, and said circuitconnecting said RC networks so that the firing of the semiconductorcurrent control element of at least one RC network energizes an adjacentnetwork to perform the series of operations in succession in apredetermined timed relation.

12. An apparatus in accordance with claim 11 in which the first RCnetwork of the plurality of networks comprises a branch circuit having asilicon control rectifier, resistor and capacitor connected in seriesacross an electric line, a unijunctional transistor connected across theline and having an emitter connected between the resistor and capacitorand which fires a predetermined period of time after the first siliconcontrol rectifier fires, and an electric responsive indicator connectedacross the line in series with a silicon control rectifier and isparallel with the RC network to indicate operation of the first step ofthe test.

13. An apparatus in accordance with claim 12 in which the electriccircuit comprises an electric responsive indicator, a branch of saidcircuit including the transistor, a pressure responsive switch and saidelectric responsive indicator connected in series for energizing theindicator when the transistor fires and the pressure operated switchremains closed to indicate a large leak in the part being tested.

14. An apparatus in accordance with claim 13 in which a second RCnetwork includes a silicon control rectifier, said electric circuithaving a branch including a pressure operated switch responsive to apressure occurring in the part being tested and connected to pulse andfire said silicon control rectifier to energize the second network whena predetermined fluid pressure occurs in said part being tested.

15. An apparatus in accordance with claim 14 in which an electricresponsive indicator is connected in parallel with said second RCnetwork whereby the indicator indicates operation of the second step ofthe test when the silicon control rectifier fires.

16. An apparatus in accordance with claim 15 in which a unijunctionaltransistor is provided having an emitter connected to the second RCnetwork and in parallel with the electric responsive device, and thetransistor being connected to energize a third RC network.

17. An apparatus in accordance with claim 16 in which the third RCnetwork includes a silicon control rectifier, and an electric responsiveelement connected in parallel with the RC network to indicate a thirdoperation of the test.

18. An apparatus in accordance with claim 17 in which the siliconcontrol rectifier in the third network is connected to an electricresponsive element for operating the divide valve to initiate a testingoperation.

19. An apparatus in accordance with claim 18 in which the meansresponsive to movement of the diaphragm is a transducer for producing avoltage directly proportional to differences in pressure in saidchambers of the measuring instrument, an electric responsive device forindicating a small leak, and said circuit having a branch including atransistor responsive to a predetermined voltage produced by saidtransducer and connected in series with said electric responsive devicefor indicating a small leak.

20. An apparatus in accordance with claim 19 in which a unijunctionaltransistor is connected to the third RC network and fires apredetermined period of time after the firing of the silicon controlrectifier, and an electric responsive indicating unit operated by thefiring of the transistor to indicate that no leak of measurablemagnitude is present in the art being tested.

21. An apparatus for testing parts for leaks comprising closure meansfor forming a chamber in the part to be tested, a source of fluid underpressure, a measuring instrument having separate chambers and atransducer for producing a voltage directly proportionally todifferences in pressure in said different chambers, conduit meansconnecting said source of pressure to the separate chambers of themeasuring instrument and chamber in the part to be tested, a fill valvefor controlling the flow of fluid in said conduit means to produce thesame pressure in the separate chambers of the measuring instrument andpart to be tested, a divide valve for isolating one chamber of themeasuring instrument from the other, an electric circuit for operatingsaid valves in sequence to perform successive testing steps, saidcircuit including a timing RC network and a semiconductor currentcontroliing device which fires a predetermined period of time afterenergization, a current responsive device in said circuit for indicatinga leak, a sensing device having a semiconductor current control elementtherein which is fired by a predetermined voltage from the transducer toenergize the current responsive device to indicate a leak, and saidtiming RC network being connected to control the period of time duringwhich the sensing device is operative to fire the semiconductor currentcontrol element therein.

22. In a testing apparatus, a measuring instrument for measuring adifference in pressure in a part being tested and a trapped sample, atransducer for producing an electric potential proportional to anydifference in pressure in the chambers of the measuring instrument, andan electric control circuit having a sensing branch with a semiconductorwhich fires when an electric potential is impressed thereon andconnected to the transducer to render it conductive when a predeterminedpotential is produced corresponding to a difference in pressure, acurrent responsive branch having an indicating element and asemiconductor which fires when an electric potential is impressedthereon, said semiconductor being directly connected to be pulsed bycurrent flow from the semiconductor in the sensing branch whereby toproduce a current flow through the indicating element and a controlbranch connected to energize the sensing branch and having an RC networkto control the period during which the sensing branch is operative toindicate a leak.

23. A leak testing apparatus in accordance with claim 22 in which themeans connected to energize the sensing branch comprises a firstsemiconductor control element, a timing branch, a second semiconductorcontrol element, and said sensing branch, timing branch and secondsemiconductor control element being connected in parallel with eachother and in series with said first semiconductor control element, saidsecond semiconductor being connected to the timing branch for producinga current flow after a predetermined period of time, a second branchcircuit having a current responsive indicating element therein and asemiconductor control element, and means for pulsing the first mentionedsemiconductor to simultaneously energize the timing and sensingbranches, said first branch circuit having a current responsiveindicating element being connected to shut off current fiow through thefirst semiconductor control element when energized, and said timingbranch circuit pulsing the second current responsive circuit if thefirst current responsive branch has not been energized.

24. An apparatus for testing parts for leaks of the type including aclosure for forming a chamber on the part to be tested, a source offluid under pressure, a measuring instrument having separate chamberswith a diaphragm therebetween, means including valves for supplyingfluid under pressure to the chamber in the part to be tested andseparate chambers in the measuring instrument and then segregating oneof the chambers in the measuring instrument at the initial fluidpressure from the other chambers, and an electric sensing circuit havinga transducer for producing a voltage directly proportional to thedifference in pressure at opposite sides of the diaphragm of themeasuring instrument, a branch circuit having a semiconductor currentcontrol element therein connected to be pulsed by the transducer uponthe occurrence of a difference of pressure in the chambers of themeasuring instrument, an electric responsive branch controlled by thefiring of the semiconductor current control element in a sensing circuitto indicate a leak in the part, said semiconductor current controlelement being a transistor and the electric sensing circuit comprising aresistance bridge connected to the outlet from the transducer andconnected to the emitter of the transistor to fire the latter when avoltage is produced by the transducer.

25. An apparatus for testing parts for leaks having a measuringinstrument for measuring any difl'erence in pressure between the partbeing tested and a closed chamber, a transducer for converting anydifference in pressure to an electric potential, an electric controlcircuit having a responsive branch including an indicating element forindicating a leak, a sensing branch connected to the responsive branchand having a normally closed switch operable to open position by apressure in the part to be tested to indicate a leak if the switch failsto open, a second sensing branch connected to the responsive branch inparallel with the first mentioned sensing branch and having a normallyopen switch operable to closed position by a rapid fall in pressure inthe part to be tested to indicate a leak, and an RC network in theelectric control circuit and connected to energize the second sensingbranch after a predetermined period of time.

26. A testing apparatus for testing parts for leaks having a measuringinstrument for measuring a difierence in pressure in a part being testedand a trapped sample, a transducer for producing an electric potentialproportional to any difference in pressure, an electric control circuithaving a current responsive branch with an indicating element and asemiconductor therein, a sensing branch connected to the currentresponsive branch and having a semiconductor connected to be pulsed anda normally closed switch operable to open position by a pressure in thepart being tested, a time delay device connected to pulse thesemiconductor in the sensing branch after a predetermined period of timeto energize the sensing and responsive branches to indicate a leak ifthe pressure operated switch fails to open, a second sensing branchconnected to the current responsive branch and having a semiconductorconnected to be pulsed and a normally open switch operable to closedposition by a fall in the pressure in the part being tested, and asecond time delay device connected to pulse the semiconductor in thesecond sensing circuit after a second predetermined period of time,whereby to energize the current responsive branch 20 to indicate a leakif the pressure falls in the part being tested.

27. An apparatus for testing parts for leaks comprising a manifold blockhaving a ballast chamber therein, a measuring instrument having separatechambers with a diaphragm therebetween and located adjacent saidmanifold block, a first conduit in said block connected to a source offluid under pressure, a second conduit in said block for connecting saidfirst conduit to said chambers of the measuring instrument, a thirdconduit in said block for connecting the first conduit to theatmosphere, a fourth conduit in said block for connecting the firstconduit to the part being tested, a fill valve in the first conduit forcontrolling the supply of fluid from said source to all of the chambers,a divide valve for isolating one of said chambers of the measuringinstrument and chamber in the manifold block from the other chamber ofthe measuring instrument and part being tested, a dump valve in thethird mentioned conduit for controlling the exhaust of testing fluidfrom the chambers, said ballast chamber being formed in said block bydrilling a hole in said block from one edge, said first and thirdconduits being formed by a hole drilled through said block parallel tothe hole forming the ballast chamber, and said second and fourthconduits being formed by a hole drilled in said block transversely ofthe first and second holes and intercepting the latter intermediatetheir ends.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,924,965 2/1960 Westerheim 7340 2,936,611 5/1960Le Mat 7340 3,031,884 4/1962 Martin 73-40 3,091,958 6/1963 Robins7346 3,221,539 12/1965 Evans 7345.2

S. CLEMENT SWISHER, Primary Examiner UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Reissue No. 26,661 September 9, 1969 RichardThomas Fitzpatrick et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 7, line 69, "2,696,556" should read 2,696,566

Signed and sealed this 30th day of March 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E SCHUYLER, JR.

Attesting Officer Commissioner of Patents

